Method of protecting an area and control system for watchman tours

Abstract

The system includes a number of spaced apart key stations which a watchman is to visit on a tour of an area. A portable unit is provided with two AND circuits. Upon starting a tour, one of the AND circuits sets a number of timers, a first one of the timers starts running providing a signal to a prealarm sound-producing device on the portable unit unless the first timer has been reset by the completion of the second AND circuit by having inserted all of the keys and turning them. At the same time, the first timer starts a second timer running. The second timer provides a delay which allows the watchman a few more minutes to complete his tour. If he fails, a third timer feeds a fault signal to a counter in the portable unit and also triggers a further audible alarm device on the portable unit and at the same time resets all the timers in the portable unit. A coder is provided in the portable unit which provided an output, via a plug and jack arrangement, to a decoder which resets a timer at a base station. Otherwise, this timer will effect the enabling of an audible alarm at the base station indicating either that all keys had not been turned or that the watchman has not returned.

I claim: 
     
       1. An alarm apparatus comprising: a plurality of fixed control keys with different combinations therebetween;   a portable control unit having a plurality of key selector switches, said selector switches being equal in number to said plurality of fixed keys and each respective one of said fixed keys corresponding to a corresponding respective one of said selectro switches;   a central unit having control means and alarm means operatively associated therewith to provide an alarm if an appropriate signal is not received within predetermined time period; and   control devices in said portable control unit which cooperate with said control means in said central unit for triggering an alarm in said portable control unit and then said alarm means in said central unit, if said appropriate signal is not produced in said portable unit within a prederermined time period, said devices in said portable unit including a signalling device which provides the appropiated signal to said portable unit and to said central control unit only when all of said fixed keys have changed all the said selector switches to a given position.   
     
     
       2. An alarm apparatus according to claim 1, wherein said control devices include means for determining if all of said selector switches have been rotated in a given direction. 
     
     
       3. An alarm apparatus according with claim 2, wherein said means for determiniing include at least one timing device which establishes maximum time of a given tour. 
     
     
       4. An alarm apparatus according to claim 3, wherein said at least one timing device includes an adjustable means for establishing the maximum time of the tour,   a second timing device to limit a time period of sounding of a prealarm signal,   a third timing device to establish a time period between the prealarm signal and an alarm signal, and   a fourth timing device to establish a time period of sounding of an alarm.   
     
     
       5. An alarm apparatus according to claim 3 or 4, wherein said control devices in said portable unit include a switch to connect and disconnect said at least one timing device. 
     
     
       6. An alarm apparatus according to claim 1, wherein each of said fixed keys activate a corresponding one of said selector switches of said portable unit, a first AND circuit is coupled to said selector switches and responds when all of said selector switches are in one of their positions and another AND circuit is coupled to said selector switches and responds when all of said lecector switches are in another of their positions, and an associated sequential network coupled to said AND circuits for producing a reset signal when a given output disappears from one of said AND circuit and appears from the other of said AND circuits. 
     
     
       7. An alarm apparatus according to claim 1, wherein said portable unit has a plug which, when inserted in a jack connected to said central unit erases time accumulated in a timing device of said central unit, said appropriate signal having been produced in said portable unit, codified in said portable unit and decodified in said central unit. 
     
     
       8. An alarm apparatus according to claim 1, wherein said control devices in said portable control unit include means for producing a prealarm signal, and timing means to trigger a second alarm, and wherein said central unit includes means for producing a third general alarm signal when the appropriate signal is not produced in said portable unit within a period of time determined by at least said timing means. 
     
     
       9. A method of protecting an area, comprising the steps of: (a) starting two predetermined time periods running, one in a portable control unit and a longer one in a central control unit;   (b) triggering respective alarms, upon expiration pf these respective periods, in the portable unit and the central unit provided that an appropiated signal has not appeared before expiration of said time periods;   (c) moving key selector switches in the portable unit to a given position within a given period to produce said appropiate signal which is to erase accumulated time of said two predetermined periods from timing devices; and   (d) connecting, via plug jack means, the portable unit with the central unit to feed said appropriate signal thereto and to erase accumulated time of the two predetermined periods from the timing devices in the portable unit and in the central unit.